1. Field of the Invention
The present invention relates to a method and apparatus for measuring an immunological antigen-antibody reaction with the aid of fluctuation in intensity of light scattered by fine particles suspended in a reaction liquid, and also relates to a measuring cell for use in such method and apparatus.
2. Related Art Statement
There has been developed an immunological analysis for measuring immune substances, hormones, medicines, and various components such as immune regulators faintly contained in living bodies by utilizing a specific immunological reaction. The immunological analysis may be roughly classified into labeling immunological analysis in which enzymes and isotopes are used as an indicator substance, and nonlabeling immunological analysis in which antigen-antibody complexes are directly measured.
In the former labeling immunological analysis, there have been widely known radio immuno assay (RIA), enzyme immuno assay (EIA) and fluorescent immuno assay (FIA). These assays have an advantage in that a high sensitivity can be attained, but also have a drawback in that handling of isotopes and waste liquid is difficult, and measuring periods are liable to be long. Further, since the labeling reagents are expensive, the test cost per sample, i.e. running cost is liable to be high.
In the latter non-labeling immunological analysis, there have been developed immuno electrophoresis, immuno diffusion and sedimentation. These methods are rather simple, but do not have sufficiently high sensitivity, quantitativeness and reproducibility necessary for precise measurement.
In "Immuno chemistry", vol. 12, No. 4 (1975), pages 349 to 351, there has been proposed an immunological analysis in which antigen or antibody bound on surfaces of fine particles are reacted with antibody or antigen contained in a test liquid, and an average diffusion constant which is an indicia of the Brownian motion of aggregates composed of agglutinated particles is measured from a variation in a spectral width of laser light scattered from a particle suspension. This method has merit in that no reagent is used. However, since the spread of the spectrum due to the Doppler effect owing to the Brownian motion of aggregates is detected by a spectrometer, the apparatus is liable to be large in size and expensive in cost. Further, error might be induced when the spectrometer is driven mechanically, so that precision and reproducibility are degraded. Moreover, in this known method, since merely the average diffusion constant is measured from the spectral width, an amount of available information about the antigen-antibody reaction is limited.